David Cameron will not attend Russian commemorations of the Allied victory in World War Two in protest at Putin's invasion of Ukraine and annexation of Crimea, Downing Street has said.

The Prime Minister will join Angela Merkel and the leaders of the Baltic states in boycotting the Victory Day parade in May, marking seventy years since the capitulation of Nazi Germany.

It is unusual for Downing Street to rule out attending an event so far in advance, not least given the event comes after the General Election on May 7, meaning Mr Cameron may not be in office. It is also unusual for Downing Street to cite a political reason for the Prime Minister’s absence at a major ceremonial event.

Britain has suspended contact between ministers and their Russian counterparts in protest at the annexation of Crimea, and the flooding of troops and weapons into eastern Ukraine. The British Government will consider sending a lower level representation.

The Prime Minister’s Deputy Official Spokesman said: "We will be considering our representation in light of our ongoing discussions with Russia, and our concerns about their activity.

"We don’t have plans for the Prime Minister to attend, and I’m sure we will set out who will represent the government in due course."

"We would consider our representation within our broader ongoing relationship with Russia. Recently, there have not been ministerial visits, and we will take that into account when we consider who attends."

Vladimir Putin had sent invitations to the parade to a host of world leaders, but has been met with refusals from the Presidents of Poland, Lithuania, Latvia, Estonia and the German Chancellor. President Obama has also refused, citing a tight schedule. Mrs Merkel will attend a wreath laying at the Tomb of the Unknown Soldier the following day.

In a re-emergence of old Cold War loyalties, the leaders of Vietnam, Serbia, the Czech Republic, China and North Korea are expected to attend.

"It will not affect the spirit, the emotional aspect and the scale of the holiday," Dmitry Peskov, Putin's spokesman said earlier, said of the apparent boycott.

Russian servicemen march during the Victory Day Parade in Moscow's Red Square

Victory Day ranks among the most important days in the Russian calendar, with more than 20 million Soviet citizens killed in the war, and is marked with a mass parade of tanks, troops and missiles on Red Square in Moscow and the overflight of dozens of jets and bombers.

It falls on May 9 – the day after Britain marks Victory in Europe Day, and two days after the General Election is held.

This year's event is likely to be highly politicised and feature the largest display of military hardware in years, including a newly formed aerobatics team named Crimean Wings.

Russian media daily compares the fighting in Ukraine to the Second World War, with claims that the Ukrainian government is a "Fascist junta" and warnings that Jewish people are in danger. The orange and black Ribbon of St George, widely associated with the Great Patriotic War, has been adopted as a symbol of the separist fighters.

David Cameron last visited Russia for the G20 summit in St Petersburg. That saw Mr Cameron launching an impassioned defence of Britain after it was dismissed by a Russian official as "just a small island".

In 1995, during the post-Cold War thaw, John Major and Bill Clinton attended commemorations in Moscow to mark fifty years since the end of the war. In 2005, John Prescott, the Deputy Prime Minister, represented Britain alongside President Bush. Tony Blair sent apologies, having only days before won a third general election.

The EU has imposed sanctions, including asset freezes and travel bans, on some 151 people and 37 entities, in response to the assault on Ukrainian sovereignty. The Foreign Secretary this week warned that Russia, which is rapidly modernising its military, as at risk of becoming the single greatest threat to British national security.